A rare form of color vision impairment in which the world is seen only in black, white, and shades of gray.

This hereditary disorder of sight is the result of a lack of cone vision; that type of vision which is provided by the cone photoreceptors in the retina.

In the normal human eye, it is estimated that there are about six million cone photoreceptors that are located largely in the center of the retina.

Lacking cone photoreceptors, people with achromatopsia must rely on their rod photoreceptors. There are approximately 100 million rod photoreceptors which are located mainly around the periphery of the retina.

Rods saturate at higher levels of illumination and do not provide color vision or good detail vision.

acyanoblepsia

The inability to discern blue colors.

acyanopsia

A color blindness towards blue.

aeluropsis

A condition of the eyes in which they are slanting.

aglaucopsia, aglaukopsia

Reduced capability, or the inability, to recognize green colors.

akinetopsia

1. Motion blindness or an inability to perceive motion, despite stationary objects remaining more or less visible, due to brain damage disrupting input to the dorsal pathway.
2. A rare neuropsychological disorder, meaning it is a disorder between the nervous system and mental functions, or in this case between the brain and perception.

In this kind of disorder, the person affected by it cannot perceive motion. It may be caused by disruption to the cortical area in the middle temporal lobe.

It can also be caused as a side effect of certain antidepressant drugs, a result of damage by a stroke, or by certain brain surgeries.

altitudinal hemianopia

Blindness in the upper or lower half of the visual field of one or both eyes.

1.The perception of having two images of a single object: An ambiopia is the double vision that exists when someone looks at something.

A person's ambiopia can be one of the first signs of a systemic disease; especially, a muscular or neurological process which may disrupt a person’s balance, movements, and/or reading abilities.

2. The status of using either eye alone at a given time: In order to avoid the simultaneous perception of two images of a single object, some people can use either the left or the right eye for each occasion.

amblyopia

1. Reduction, or dimness, of vision; especially, that in which there is no apparent pathologic condition of the eye.
2. Impairment of vision without detectable organic lesion of the eye.
3. Poor vision caused by abnormal development of visual areas of the brain in response to abnormal visual stimulation during early development.